In this passage, we have two substantive changes. In the 1874 RLDS edition, the preposition unto was omitted, probably accidentally. The 1908 RLDS edition restored the original preposition to the RLDS text. For a similar example, see under Alma 11:22; in that instance, the 1830 typesetter accidentally omitted the unto from “and all these will I give unto thee”.
The second substantive change here in Alma 26:27 is more significant. In his editing for the 1837 edition, Joseph Smith emended the singular thee to the plural you. (I ignore the 1830 compositor’s mis-setting of thee as the, a nonsubstantive change in the text.) Note, however, that Joseph did not change the preceding thy and thine to your. In this passage, the Lord is speaking to the sons of king Mosiah, a plurality. But as explained under 1 Nephi 3:29, the original text of the Book of Mormon sometimes allowed the historically singular pronoun thou to be used in the plural. The critical text will therefore restore the thee to this passage in Alma 26:27. For a complete list of passages that originally used the second person singular pronoun for plurals, see under thou in volume 3.
Summary: Restore in Alma 26:27 the historically singular thee since this is the reading of the earliest textual source, the printer’s manuscript; also maintain the preposition unto before thee.